I know that it's really like 708.75 power, minus about 4-5 HP. In the damage formula, STAB and the sun boost a +2 (like, add on 2 HP to the damage) while the special attack boosts don't. If that +2 didn't exist, the 1.5 boost to special attack would result in a 1.5 boost in the damage, and little cup wouldn't be so offensive especially in gen 4.uhmm.. it doesnt seem like you have a grasp of what things get boosted by 1.5. overheat is boosted by stab, and the sun, hitting for 315 base power. charizards special attack stat is boosted by specs and solar power. to think you actually believed a 4x resisted overheat would hit for about 175 power makes me laugh.
I have found scarf Hihidaruma tears through many of my teams with Flare Blitz(just not my rain team), while Fire Punch on those guys is a failure.